By default, the Outlook folder list groups similar folders, such as inboxes, from all of your mail and Microsoft Exchange accounts. This feature can make it easier to read all your messages at once, without having to move between mail folders. If you want, you can turn off this feature so each account and all its folders are separated in the folder list.
On the Outlook menu, click Preferences.
Under Personal Settings, click General .
Under Sidebar, clear the Show all mail account folders check box.